Manufacture of electrical condensers



May 7, 1945 R. A. GRoUsE ET AL 2,399,"798

May 7, 1946- R. A. GRoUsE ET AL. 2,399,798

MANUFACTURE OF ELECTRICAL CONDENSERS Filed July 8, 194:5 2 sheetsfsheeteNVINTGRS Rmmzo ALFRED Gnomi l and JAM Romke.v

Patented May 7, 1946 MANUFACTURE OF ELECTRICAL CONDENSERS Richard AlfredGrouse andk James Rogers- Londoni, England, asslgnors to A. H. HuntLimited, London, England, a British company Application July 8, 1943,Serial No. 493,824 In Great Britain July 13, 1942 This invention relatesto the manufacture of electrical condensers. Metallised paper, i. e.paper having the metal in the form of a film or thin layer on onesideonly of the paper, is known for use in the manufacture ofcondensers, the thinness of the metallised paper enabling condensers yto be made having a high capacity and yet; compact in form and light inweight.

In making such' condensers by a process as described in co-pendingUnited State' patent application Serial No. 493,172 it is necessary tosupply to the winding machine, two strips of paper with an unmetallisededge, the two strips being of opposite hand, that is to say, looking atthe metallised side of the paper as fed to the winding machine, theunmetallised margin must be on the left of one strip and on the right ofthe other. It is not economical to manufacture strips of paper with ametallised surface and an unmetallised margin directly in th'e form ofsuch strips; it is preferable that wide rolls of paper, such as aresupplied by paper manufacturers, should be treated for metallisationover their area considered as a whole. It is an object of the presentinvention to facilitate the provision of strips of paper having anunmetallised margin along one edge in such form as can be readily woundinto condensers of 'the kind desired.

The present invention comprises in the manufacture of electricalcondensers from metallised dielectric strips wound together, each striphaving an unmetallised margin, the combination of steps for preparingthe strips which consists in rst preparing a wide strip of metalliseddielectric in a form in which bands of metallisation alternate withunmetallised bands, the bands extending along the length ofthe strip,and then slitting the wide strip along the centre lines of theunmetallised bands and also along lines within the metallised bands.

This provides a plurality of strips of paper of the desired width' eachhaving an unmetallised margin, and alternate strips, as cut from thepa-A per, are automatically of opposite hand Pairs of such strips aretaken and then wound into condensers by any desired method, for examplethatl the known process of making Mansbridge foil.

Alternatively the paper may be metallised by any desired process such asthat described in the United States Patent No. 2,100,045 and the actualprocess of metallisation forms no part of the present invention.

The invention includes in the manufacture of electrical condensers frommetallised dielectric strips wound together, each strip having anunmetallised margin, the combination of steps for preparing the stripswhich consists in rst metallising a wide strip of dielectric across itswhole width, then removing the metal film in bands along the length ofthe strip, and then slitting the wide strip along the centre lines ofth'e demetallised bands and also along lines within the metallisedbands.

For slitting the paper any known form of paper slitting machine may beused, or the band may be slit in its passage from one roll to anotherroll, or plurality of rolls, by grow of stationary knives held in thepath of the band, or it may be slit when on a roll by pressing a row ofknives against the rotating roll.

Conveniently, electrical faults in the paper may be burnt out during theslitting operation by passing the paper past electrified rollers on itsway to the slitting knives.

The following is a description, by way of example, of one apparatus forcarrying the invention into effect and of the process of the inventionas carried out therein, reference being made to the accompanyingdrawings in which:

Figure 1 is a diagram of the process and albparatus showing only theessential working parts;

Figure 2 is aplan of part of the apparatus, Figure 1;

Figure 3 shows a pair of rolls of paper, rightand left-hand, when slit;

Figure 4 is a diagrammatic representation of the winding of a condenserfrom the rolls of Figure 3;

Figure 5 shows the step of the process of demetallising strips upon thepaper prior to the passing of the paper through the apparatus of Figurel.

Referring to the diagram, a roll of paper H is taken which has beenmetallised on one face, for example by the process described in theaforesaid United States Patent No. 2,100,045. 'I'he metallisation mayconsist of any desired metal, such as copper or, preferably, aluminiumand is exceedingly thin but electrically conductive. The metallisationis effected in bands I2 and between the metallised bands there areunmetallised bands I3 which are indicated by broken lines in thedrawings (Figure 2) as they do not correspond with any discontinuity inthe paper and in the part of the figure where the paper is flat themetallisation is on the underside of the paper. The unmetallised bandsmay be produced in the metallising process by screening portions of thepaper or they may be produced by removing the metallised surface afterit has been applied; for example in the case of the metallised layerbeing produced by the known process of making Mansbridge" foil theunmetallised bands may be produced by removing the metal as described incopending United States patent application Serial No. 493,173, and ashereinafter described in connection with Figure 5 hereof.

The roll of metallised paper I I may conveniently be supported on acentral cardboard tube I4 which is slid on to a supporting spindle I5and the spindle |5 is provided with an appropriate mounting forrotation, not shown in the drawings.

From the roll the paper passes under an electrified metallic electroderoller 2|, in a nearly horizontal direction, then over and in contactwith an earthed metallic electrode roller 22 the two rollers beingmaintained at a potential-difference relative to one another equal tothe test voltage which it is desired to apply to the paper of thedielectric. Thence the paper passes under another electrified roller 23,over a second earthed roller 24 and a third electrified roller 25.

The potential of the electrified rollers 2|, 23, 25 relative to therollers 22, 24 may be, say 600 volts. This figure suits for use in thecase of paper which has an extremely thin metallised aluminium or coppersurface, the thinness of the paper being about four ten-thousandths ofan inch. The speed of passage of the paper is about two feet per second.Under these conditions the metallised bands are maintained at earthpotential while a potential of 600 volts is applied to the opposite faceof the paper. Any faults in the paper dielectric cause communicationbetween the metallised surface and the electrified rollers; owing to theextreme thinness of the metallisation the effect is that current passingthrough the metal to the fault becomes concentrated at the fault and themetallised surface immediately around the fault is vaporised anddisappears, thereby eliminating the fault. Even the best hard glazedwaxed paper if made of the thinness referred to possesses numerousfaults against a test voltage as high as 600 and as the paper cornes incontact with the first electrified roller 22 a line of sparks orscintillations which indicate the burning out of the faults appears atthe ongoing line of contact of the paper with the roller. Some faultswill still remain in the paper after leaving the roller 22 but suchfaults will be eliminated as they pass the other rollers.

In some cases, especially where exceptionally thin paper is employed, itmay be desirable to employ a larger number of electrified rollers.Alternatively the paper may be run through the electrified rollers morethan once and rewound before being finally run through and slitted, andin this case the speed of travel of the paper may be increased, as anyfaults which are not eliminated on the first passage through theapparatus can be eliminated in a second or third passage.

After the elimination of faults the paper is slit. For this purpose anydesired slitting machine may be adopted, usually having a gang of knivesto make all the slits simultaneously. The arrangement in the drawings isdiagrammatic only and shows the paper being wound on to a spindle 41parallel to a knife-supporting bar 66. On the bar 66 is a block 61carrying a knife 68 and handle 69. The knife can be brought to anydesired position opposite the roll of paper after it has been wound and,the roll of paper being driven by a belt on a pulley 52. the knife canbe applied to the roll and will cut into the paper 5 along a slit-linesuch as the line 50 of Figure 2. One cut is madeat a time completelythrough to the shaft by lifting the handle 60 and then the block 61 isslid along the bar 66 into position to take another cut. If the blade 69is made of thin l sheet steel the roll of paper can be satisfactorilyslit in this manner.

'A cut is made down each metallised band I2 and also down the middle ofeach unmetalllsed band I3. Where bands of equal width are rel quired,the cuts are down the middle of the metallised bands, as shown. Thisproduces a number of rolls 45 which, as viewed from the end of theapparatus towards which the paper is travelling, have an unmetallisedmargin on the lefthand side and a further series of rolls 46 which havean unmetallised margin on the right-hand side.

One of the left-handed rolls 45 thus produced and one of theright-handed rolls 46 are shown together in Figure 3. Tl'iese rolls aretaken and are wound together to produce a condenser in the mannerindicated in Figure 4, that is to say with the insulated margins of therolls of paper serving to ensure separation of the two metallisedsurfaces which constitute electrodes of opposite polarity. In Figure 4the dielectric of one strip is indicated by a full line at 45 and thedielectric of the other strip is indicated at 46, the two dielectricsbeing interleaved. The

metallised surface is diagrammatically indicated by chain lines 6|, 62respectively and it will be seen that the unmetallised margins serve toinsulate the metallised portions from each other. The metallisedportions of the strips which project at the ends of the roll are ofopposite polarity and provide terminals. Conveniently they may be turnedover in winding as indicated in Figure 4 so as to present theirmetallised surfaces endwise and facilitate making electrical connectionsste them. A method of effecting this winding of the condensersautomatically is described in copending United States patent applicationSerial No. 493,172. y

Referring now to Figure 5, this shows a roll of tin-coated paper |20being fed towards a spindie |2| mounted in bearings |22, |23 and drivenby a belt on a pulley |24. The spindle |2| therefore draws the papertowards itself and winds it into a roll |25. In the course of itspassage the paper passes beneath a spindle |26 supported in bearings|21, |28. On the spindle |26 there are a. number of copper discs |30which are supported on heat insulating bosses |3| and have electricalheating elements |32 clamped against 50 their side. The heating elements|32 are supplied with electric current by means of tWo slip rings |33,|34 and brushes |35, |36, The edges |31 of the discs |30 are tinned andare brought to a sufficient heat to melt the tin coating on the 55 paperweb when they engage it. For this purpose the tin-coated side of thepaper must be passed so as to be uppermost and thus to come in contactwith the discs and the speed of the spindle |2| is made controllable sothat the speed of passage of the paper may be kept at a suitable rate,so that the paper is not scorched although the tin is effectivelyremoved. The rim portions |31 of the discs |30 are made of such a widththat they correspond to the width of the strip which is to bedemetallised along the length of accesos the paper web I2! and thespacing of the copper discs is such that they demetallise a number ofstrips of the desired width as the paper comes in contact with them inthe course of its progress; the demetallised strips are indicated in thedrawing at ill. Excess of tin can be removed from the discs |30 fromtime to time by applying a wiper thereto while they are rotating andthus no stoppage of the apparatus for removal of tin is necessary.

In order that lthe heated rotating rollers may effectively demetallisethe paper it is desirable that the paper should. before being passedthrough the apparatus of Figure 5, be impreg nated with ilux. A suitableilux consists of a mixture ofpetroleum jelly 80% and resin 20%, meltedtogether and applied to the paper before the application of the tincoating thereto. The paper is coated with the tin by any well knownY ordesired process such as that in common use for making tin-coated paperfor the manufacture of "Mansbridge condensers. The process ofdemetallisation per se is claimed in co-pending United States patentapplication Serial No. 493,173.

It is an important advantage of the present invention that as the,metallised bands I2 in the original web of paper are cut through, themetallised portions of the cut strips are fully metallised right up tothe edge. If the paper were originally selected with metallised andunmetallised bands' of the same width only as that desired for the rollswhich are to be Wound into the condenser, the paper would have to beslit along the line of Junction between an unmetallised band and ametallised band and there would be risk of the edge of the metallisedportion of -the paper not being fully metallised up to its edge, and ofthe unmetallised margin left on the adjacent strip carrying here andthere a partially metallised portion which would interfere with theinsulation of the condenser. Moreover as this risk is lremoved it ispossible to make the strips with narrower insulating margins, the designof the condenser is more emcient, and the capacity larger for a givensize.

We claim:

A process for the manufacture of an electrical wound paper condensercomprising in combination the steps of first selecting a wide strip ofpaper metallized over its whole width, then removing bands of metaltherefrom so as to leave metallized bands alternating with unmetallizedbands, slitting the wide strip along the center lines of theunmetallized bands and also along lines which divide the metallizedbands longitudinally, rolling the resulting strips into alternate"right-handed" and "left-handed rolls, selecting a right-handed and aleft-handed roll so produced and winding together strips from each rollwhereby thin unmetallized edges lie toward opposite ends of thewoundcondenser,

the strips being wound without any interleaving strips and so that eachunmetallized edge is overlapped by the metallized edge of Vthe adjacentstrip.

RICHARD ALFRED GROUSE. JAMES ROGERS.

